Draw a diagram for this Galvanic cell, labeling the electron flow, the anode and cathode, and the positive and negative sides of the Galvanic cell?

A Galvanic cell runs on the following reaction:
#Co (s) + Cu^(2+) (aq) -> Co^(2+) (aq) + Cu (s)#

Draw a diagram for this Galvanic cell, labeling the electron flow, the anode and cathode, and the positive and negative sides of the Galvanic cell.

1 Answer
Apr 4, 2018

Answer:

Explanation:

From the reaction formula:
Copper is reduced as its oxidation state decreases from #+2# in #Cu^(2+)(aq)# to #0# in #Cu(s)#.
Cobalt is oxidized; its oxidation state increases from #0# in #Co(s)# to #+2# in #Co^(2+)(aq)#

Direction of electron flow
An element gains electrons as it undergoes reduction and loses electron when it undergoes oxidation. Therefore there's going to be a flow of electron from cobalt to copper through the external circuit.

Anode or cathode
"The cathode is where the reduction take place and oxidation takes place at the anode". (Chemistry Libretexts) [2]
Cobalt is being oxidized to form cobalt (II) ions so the cobalt electrode would be the anode. Copper (II) ions are reduced to elementary copper at the copper electrode, so that would be the cathode.

The way I memorize this is by considering where the two names for the voltaic electrodes came from. The #color(blue)("An")"ode"# of a cell, voltaic or electrochemical, attracts anions (ions with negative charges) and thus must carries some positive charges. So it is losing electrons and thus undergoing oxidation. Similarly, the #color(red)("Cat")"hode"# attracts cations (positively-charged ions), possesses excessive negative charges and therefore undergoes reduction. It's apparently a rule of thumb but it works for me.

Positive or negative terminal
Electrons always flow from the negative terminal to the positive terminal- exactly the opposite as the direction of the current flow. Therefore the cathode would be the positive terminal and the anode the negative terminal.

References
[1] "Galvanic Cells", CK-12 Editor, https://www.ck12.org/section/Galvanic-Cells/

[2] "Voltaic Cells", LibreText Chemistry, https://chem.libretexts.org/Core/Analytical_Chemistry/Electrochemistry/Voltaic_Cells